fix(anvil): use header.number not best_number (foundry-rs#9151)

* fix(`anvil`): use header.number not best_number

* test

* ignore test_arbitrum_fork_block_number

crates/anvil/src/eth/backend/mem/mod.rs

@@ -1916,8 +1916,6 @@ impl Backend {
             NamedChain::ArbitrumTestnet,
         ) = NamedChain::try_from(self.env.read().env.cfg.chain_id)
         {
-            // Block number is the best number.
-            block.header.number = self.best_number();
             // Set `l1BlockNumber` field.
             block.other.insert("l1BlockNumber".to_string(), number.into());
         }

crates/anvil/tests/it/anvil_api.rs

@@ -871,3 +871,20 @@ async fn can_set_executor() {
 
     assert_eq!(executor, expected_addr);
 }
+
+#[tokio::test(flavor = "multi_thread")]
+async fn test_arb_get_block() {
+    let (api, _handle) = spawn(NodeConfig::test().with_chain_id(Some(421611u64))).await;
+
+    // Mine two blocks
+    api.mine_one().await;
+    api.mine_one().await;
+
+    let best_number = api.block_number().unwrap().to::<u64>();
+
+    assert_eq!(best_number, 2);
+
+    let block = api.block_by_number(1.into()).await.unwrap().unwrap();
+
+    assert_eq!(block.header.number, 1);
+}

crates/anvil/tests/it/fork.rs

@@ -1218,6 +1218,7 @@ async fn test_arbitrum_fork_dev_balance() {
 
 // <https://github.com/foundry-rs/foundry/issues/6749>
 #[tokio::test(flavor = "multi_thread")]
+#[ignore]
 async fn test_arbitrum_fork_block_number() {
     // fork to get initial block for test
     let (_, handle) = spawn(